Thermal conductivity of boron arsenide above 2100 watts per meter per Kelvin at room temperature

TL;DR

This study reports a record-high thermal conductivity in boron arsenide crystals exceeding 2100 W/mK at room temperature, achieved through impurity reduction, and explores phonon scattering mechanisms affecting heat transport.

Contribution

It demonstrates a significant increase in boron arsenide's thermal conductivity by impurity control and highlights the need for revised theoretical models of phonon scattering.

Findings

Thermal conductivity exceeds 2100 W/mK at room temperature.

Thermal conductivity follows a T-1.8 dependence, indicating dominant four-phonon scattering.

Modified theoretical calculations fit experimental data by adjusting three-phonon scattering.

Abstract

Boron arsenide (BAs) single crystals had been previously reported to have thermal conductivity of 1500 W/mK at room temperature. Now we achieved thermal conductivity above 2100 W/mK at room temperature in BAs crystals due to much lower concentration of impurities Si, C, and O grown from purified arsenic. We also observed a T-1.8 dependence of the thermal conductivity, suggesting a more significant contribution from four-phonon scatterings than suggested by previous theory. We found that our experimental result can be fit with a modified theoretical calculation by tuning down the three-phonon scattering for phonons in the 4-8 THz range, although current phonon transport theory cannot provide a physical explanation. Such an advance will not only attract more effort on growing BAs single crystals and studying their practical applications but also stimulate theoretical work to predict more materials with possibly even higher thermal conductivities.